KR101927722B1 - A vapor permeable membrane and a method for manufacturing the same - Google Patents

Abstract

One embodiment of the present invention provides a vapor permeable membrane comprising: an intermediate porous layer and a surface porous layer located on at least one side of the intermediate porous layer, wherein the average pore diameter (d_1) of the intermediate porous layer and the average pore diameter (d_2) satisfy the following conditions (i) and (ii): (i) d_1 > d_2, (ii) d_1 - d_2 >= 5 nm.

Description

TECHNICAL FIELD [0001] The present invention relates to a vapor permeable membrane and a vapor permeable membrane,

The present invention relates to a vapor-permeable membrane and a method of manufacturing the same, and more particularly, to a vapor-permeable membrane having a predetermined average pore diameter along a thickness direction and a method of manufacturing the same.

The transport of volatiles, such as fragrances, air fresheners, can be accomplished by a transport device comprising a reservoir containing volatile materials. The transport device typically includes a vapor permeable membrane that covers or surrounds the reservoir. Volatile substances in the reservoir pass through the vapor permeable membrane and are released into the air. Vapor permeable membranes are typically made from organic polymers and are porous.

In general, the rate at which volatile substances pass through the vapor permeable membrane is an important factor. For example, if the rate at which the volatile material passes through the vapor permeable membrane is too low, it will be very difficult to detect it because the fragrance is very weak. On the other hand, if the rate at which the volatile substance passes through the vapor permeable membrane is too high, the volatile substance may be quickly depleted and the fragrance may be very strong, which may cause discomfort to the user.

Further, when the ambient temperature rises, the rate at which the volatile substance passes through the vapor permeable membrane may become unnecessarily high. For example, a transportation device used inside a passenger compartment of a vehicle may be exposed to an ambient temperature rise, and accordingly, it is necessary to control when the rate at which volatile substances contained in the transportation device pass through the vapor permeable membrane increases .

It is an object of the present invention to provide a vapor permeable membrane capable of preventing sudden outflow and loss of volatile substances by controlling the flow and volatilization amount of volatile substances to a necessary range, And a method for manufacturing the same.

One aspect of the present invention is directed to a microporous membrane comprising an intermediate porous layer and a surface porous layer disposed on at least one side of the intermediate porous layer, wherein the average pore diameter (d ₁ ) of the intermediate porous layer and the average pore diameter (d ₂ ) satisfy the following (i) and (ii).

(i) d ₁ > d ₂ , (ii) d ₁ - d ₂ ≥ 5 nm.

In one embodiment, the intermediate porous layer and the surface porous layer may be integrally formed.

In one embodiment, the vapor-permeable membrane may be made of a resin composition comprising a polyolefin.

In one embodiment, the polyolefin may be one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and mixtures or copolymers of two or more of the foregoing.

In one embodiment, the polyolefin may be an ultra high molecular weight polyethylene having a weight average molecular weight of 200,000 to 1,000,000 and an intrinsic viscosity of 5.0 dl / g or more.

In one embodiment, d ₁ may range from 65 to 300 nm and d ₂ may be less than 60 nm.

In one embodiment, the thickness of the vapor-permeable membrane may be 20 to 1,200 microns.

In one embodiment, the thickness of the surface porous layer may be 1 to 50% of the thickness of the vapor permeable membrane.

According to another aspect of the present invention, there is provided a method for producing a base sheet, comprising: (a) extruding a resin composition comprising a polyolefin and a pore-forming agent, discharging the resin composition through a Ti-die, (b) passing the base sheet through a calender roll to impart a gradient to an average pore diameter along a thickness direction of the base sheet; And (c) dipping the base sheet in a solvent to remove the pore-forming agent, wherein an operation speed of the casting roll is not less than a discharge speed of the Ti-die.

In one embodiment, the polyolefin may be one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and mixtures or copolymers of two or more of the foregoing.

In one embodiment, the polyolefin may be an ultra high molecular weight polyethylene having a weight average molecular weight of 200,000 to 1,000,000 and an intrinsic viscosity of 5.0 dl / g or more.

In one embodiment, the running speed of the casting roll may be at least 1.1 times the discharge speed of the T-die.

In one embodiment, the average pore diameter along the thickness direction of the base sheet in the step (b) may satisfy the following (i) and (ii).

(i) d ₁ > d ₂ , (ii) d ₁ - d ₂ ≥ 5 nm,

In the above (i) and (ii), d ₁ is the average pore diameter of the intermediate porous layer, and d ₂ is the average pore diameter of the surface porous layer located on at least one side of the intermediate porous layer.

In one embodiment, the pore former is selected from the group consisting of paraffin oil, paraffin wax, mineral oil, solid paraffin, soybean oil, rape oil, palm oil, palm oil, di- , Bis (2-propylheptyl) phthalate, naphthenic oil, and mixtures of two or more thereof.

In one embodiment, in step (c), the solvent may be selected from the group consisting of pentane, hexane, benzene, dichloromethane, carbon tetrachloride, methyl ethyl ketone, acetone, and mixtures of two or more thereof.

According to an aspect of the present invention, a predetermined gradient is given to the average pore diameter along the thickness direction of the vapor permeable membrane to appropriately control the movement and flow rate of the volatile substance through the vapor permeable membrane.

It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be deduced from the description of the invention or the composition of the invention set forth in the claims.

1 is a schematic cross-sectional view of a vapor-permeable membrane according to an embodiment of the present invention.
2 is a graphical illustration of the amount of volatile material carried on a vapor permeable membrane according to an embodiment of the present invention.
3 illustrates the movement of volatile materials through a vapor permeable membrane according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Vapor permeable membrane

1 is a schematic cross-sectional view of a vapor-permeable membrane according to an embodiment of the present invention. 1, the vapor-permeable membrane according to one embodiment of the present invention includes an intermediate porous layer 200 and a surface porous layer (not shown) disposed on at least one surface, preferably both surfaces, of the intermediate porous layer 200 100) can be included, and to satisfy the average pore diameter (d ₁₎ and to the average pore diameter (d ₂₎ of the surface porous layer (100) (i) and (ii) of the intermediate porous layer (200) .

(i) d ₁ > d ₂

(ii) d ₁ - d ₂ ≥ 5 nm

The pores of the intermediate porous layer 200 and the surface porous layer 100 of the vapor permeable membrane can be connected and communicated through the vapor permeable membrane to form a network, Volatiles can move.

As used herein, the term "volatile material" is intended to include any material that can be converted to a gaseous form or vapor form at ambient temperatures and pressures, without the added or supplementary energy imparted, e.g., heat and / , ≪ / RTI >

Volatile materials may include those dispersed in organic volatile materials or solvent-based materials that may include volatile materials including solvent-based materials. The volatile material may be in liquid form and / or solid form, and may be naturally occurring or artificially synthesized. In the solid form, the volatile material is typically sublimed from the solid form to the vapor form, without the liquid form being the intermediate. The volatile material may be optionally combined or blended with a non-volatile material, e.g., a carrier, e.g., water and / or a non-volatile solvent. In the case of solid volatiles, the non-volatile carrier may be present in the form of a porous material, for example, a porous inorganic material, to which the solid volatiles are immobilized. In addition, the solid volatile material may be in the form of a semi-solid gel.

The volatile material may be a perfume material, for example, a naturally occurring oil or a synthetic perfume oil. Perfume oils from which liquid volatiles may be selected include perfume oils such as bergamot oil, citrus oil, lemon oil, mandarin oil, caraway oil, leaf oil, cinnabar oil, cedar oil, geranium oil, lavender oil, But are not limited to, one selected from the group consisting of petit grain, linseed oil, parsley oil, neroli oil, rose oil absolute, and combinations of two or more thereof. Solid fragrance materials that may be selected as volatile materials include, but are not limited to, vanillin, ethyl vanillin, coumarin, tonalide, calon, heliotrofen, musk xylol, sedol, musk ketone benzophenone, lusspur ketone, methylnaphthyl ketone beta, Phenylethyl salicylate, benzyl alcohol, maltol, maple lactone, pro-eugenol acetate, epobalm, and combinations of two or more thereof.

When the vapor permeable membrane includes the intermediate porous layer 200 and the surface porous layer 200 located on both sides of the intermediate porous layer 200, It is possible to contact the intermediate porous layer 200 through the porous layer 100 and the introduced volatile substance can be introduced into the intermediate porous layer 200 through the intermediate porous layer 200, And the surface porous layer 200 located on the other surface of the intermediate porous layer 200. [

That is, the surface porous layer 100 located on one side of the intermediate porous layer 200 faces the volatile substance contained in the reservoir and preferably constitutes a contact surface contacting the volatile substance, and the intermediate porous layer The surface porous layer 100 located on the other side of the reservoir 200 may constitute a discharge surface where the volatile material does not face and / or contact the volatile material contained in the reservoir and from which the volatile material flows out in vapor or vapor form.

The average pore diameter (d ₁₎ and the moving speed of the average pore is greater than the diameter _{(d 2) (d 1>} d 2), the volatile material of the surface porous layer (100) of the intermediate porous layer 200 is the surface And may be faster in the middle porous layer 200 than in the porous layer 100.

The volatile material can be introduced at a constant rate through the surface porous layer 100 constituting the contact surface, and the moving speed of the volatile material can be increased in the middle porous layer 200 having an average pore size relatively larger than the contact surface . However, when the volatile substance reaches the surface porous layer 100 constituting the discharge surface, the average pore size of the volatile substance is smaller than that of the intermediate porous layer 200, the moving speed of the volatile substance may decrease again.

The surface porous layer 100 constituting the discharge surface stagnates the movement of the volatile substance accelerated through the contact surface and the intermediate porous layer 200, specifically, the outflow and the volatilization, Layer 200 as shown in FIG. In addition, the average pore diameter (d - ₂ ) of each of the surface porous layers 100 constituting the contact surface and the discharge surface may be substantially the same.

However, if the difference between the average pore diameter (d ₂₎ of the average pore diameter (d ₁₎ and the surface porous layer (100) of the intermediate porous layer 200 is less than _{5nm (d 1 - d 2 <} 5nm), the The migration characteristic of the volatile substance in the vapor permeable membrane, specifically, the inflow, the carry and the outflow may not be smooth. Particularly, volatile substances are not supported on the middle porous layer 200, but are flowed into the vapor permeable membrane and flowed out and volatilized. As a result, volatile substances are quickly depleted and fragrance is very strong, which may cause inconvenience to the user. Thus, the difference between the average pore diameter (d ₂₎ of the average pore diameter (d ₁₎ and the surface porous layer (100) of the intermediate porous layer 200 is at least _{5nm (d 1 - d 2 ≥} 5nm) preferably in the Do. In this case, d ₁ and d ₂ may be, for example, 65 to 300 nm and 10 to 60 nm, respectively.

FIG. 2 is a graphical representation of the amount of volatile substances carried on the intermediate porous layer of the vapor-permeable membrane according to an embodiment of the present invention. FIG. 3 illustrates the movement of volatile materials through the vapor- It is.

Referring to FIGS. 2 and 3, the volatile material flows into the vapor permeable membrane through the surface porous layer 100 constituting the contact surface in the interval t ₀ to t ₁ , and is carried on the intermediate porous layer 200 . As described above, since the surface porous layer 100 constituting the discharge surface acts as a barrier for decreasing the moving speed of the volatile substance, the amount of volatilized substance carried increases, and when t ₁ is reached, the middle porous layer 200 ) of the pores of the volatile substances it is completely supported on a, t ₁ after which the air to the flow rate and the volatiles constant speed to discharge reaches the same steady state (steady state) of the volatile substances on the basis of the intermediate porous layer (200) Outflow, and volatilization. After t ₂ , the amount of volatile substances to be loaded decreases. This is because the volatile substance facing or contacting the contact surface is completely exhausted and is no longer introduced into the vapor permeable membrane, Volatilized material flows out through the discharge surface and is volatilized.

Referring again to FIG. 1, the intermediate porous layer 200 and the surface porous layer 100 may be formed by joining independent layers, respectively, and may be integrally formed, if necessary. Preferably, the intermediate porous layer 200 and the surface porous layer 100 constituting the vapor permeable membrane may be integrally formed, and the average pore size of the vapor permeable membrane may be determined by a predetermined method or process, It may be that the diameter is given a gradient.

The vapor permeable membrane may have a thickness of 20 to 1,200 m. If the thickness of the vapor permeable membrane is less than 20 μm, the physical properties of the membrane may be deteriorated. If the thickness of the vapor permeable membrane is more than 1,200 μm, the membrane may be thickened to decrease the permeability.

Also, the thickness of the surface porous layer 100 may be 1 to 50% of the thickness of the vapor permeable membrane. If the thickness of the surface porous layer is less than 1% of the thickness of the vapor permeable membrane, the flow through the contact surface is not smooth and the discharge surface acts as a barrier against volatile substances moving through the middle porous layer 200 If the ratio is more than 50%, the thickness of the middle porous layer 200 is relatively decreased, and volatile substances flow into the vapor permeable membrane and simultaneously flow out and volatilize. As a result, the volatile substances are quickly depleted and the fragrance is very strong. can do.

The vapor permeable membrane may be made of a resin composition containing a polyolefin. The polyolefin may be one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and mixtures or copolymers of two or more thereof, preferably polyethylene, Preferably, it may be an ultrahigh molecular weight polyethylene having a weight average molecular weight of 200,000 to 1,000,000 and an intrinsic viscosity of 5.0 dl / g or more, but is not limited thereto. In addition, the resin composition may further include one inorganic additive selected from the group consisting of silica, TiO ₂ , zirconia, alumina, and combinations of two or more thereof. The inorganic additive absorbs, adsorbs, or collects volatile substances permeating through the vapor permeable membrane, so that the residence time of the volatile substance in the vapor permeable membrane can be increased and the durability and mechanical properties of the vapor permeable membrane can be enhanced.

Method for producing vapor permeable membrane

A method for manufacturing a vapor-permeable membrane according to another aspect of the present invention includes the steps of: (a) extruding a resin composition comprising a polyolefin and a pore-forming agent, discharging the resin composition through a Ti-die, ; (b) passing the base sheet through a calender roll to impart a gradient to an average pore diameter along a thickness direction of the base sheet; And (c) dipping the base sheet in a solvent to remove the pore-forming agent.

In the step (a), a resin composition containing a polyolefin and a pore-forming agent may be extruded and discharged through a Ti-die, and then passed through a casting roll to produce a base sheet.

The polyolefin may be one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and mixtures or copolymers of two or more thereof, preferably polyethylene, Preferably, it may be an ultrahigh molecular weight polyethylene having a weight average molecular weight of 200,000 to 1,000,000 and an intrinsic viscosity of 5.0 dl / g or more, but is not limited thereto.

Wherein the pore former is selected from the group consisting of paraffin oil, paraffin wax, mineral oil, solid paraffin, soybean oil, rape oil, palm oil, palm oil, di- Heptyl) phthalate, naphthenic oil, and a mixture of two or more thereof. Preferably, it may be an alkyl phthalate, more preferably bis (2-propylheptyl) phthalate, But is not limited thereto.

The resin composition may further include one inorganic additive selected from the group consisting of silica, TiO ₂ , zirconia, alumina, and combinations of two or more thereof. The inorganic additive absorbs, adsorbs, or collects volatile substances permeating through the vapor permeable membrane, so that the residence time of the volatile substance in the vapor permeable membrane can be increased and the durability and mechanical properties of the vapor permeable membrane can be enhanced.

The resin composition may be melt-extruded through an extruder, preferably a twin-screw extruder, discharged through the Ti-die, and then passed through the casting roll to be made into a base sheet. In this case, the ejecting speed of the tee-tie may be 0.5 to 1.0 m / min, and the operating speed of the casting roll may be at least 1 times, preferably at least 1.1 times, Can be adjusted to 1.1 to 2.0 times. By adjusting the operation speed of the casting roll faster than the discharge speed of the Ti-die, it is possible to substantially extend the base sheet without introducing a separate stretching process of the base sheet, for example, a uniaxial stretching or a biaxial stretching process And thus a pore of a predetermined size can be formed in the vapor permeable membrane.

In the step (b), the base sheet may be passed through a calender roll to impart a gradient to the average pore diameter along the thickness direction of the base sheet. The running speed of the calender roll can be adjusted to be substantially equal to the running speed of the casting roll.

The gradient of the average pore diameter along the thickness direction imparted to the base sheet by the step (b) may satisfy the following (i) and (ii).

(i) d ₁ > d ₂

(ii) d ₁ - d ₂ ≥ 5 nm

In the above (i) and (ii), d ₁ is the average pore diameter of the intermediate porous layer, and d ₂ is the average pore diameter of the surface porous layer located on at least one side of the intermediate porous layer. The gradient of the average pore diameter, its range, and its action and effect are the same as described above.

In the step (c), the base sheet is immersed in an extraction vessel having a solvent, and the pore-forming agent is extracted and removed to obtain a vapor permeable membrane. The extraction temperature may be from 20 to 40 캜, and the extraction time may be from 1 to 20 minutes. The solvent may be selected from the group consisting of pentane, hexane, benzene, dichloromethane, carbon tetrachloride, methyl ethyl ketone, acetone, and mixtures of two or more thereof, preferably dichloromethane, but is not limited thereto .

Hereinafter, embodiments of the present invention will be described in detail.

Example 1

860 g of ultrahigh molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 400,000 and an intrinsic viscosity of 5.1 dl / g, 1,161 g of silica and 129 g of TiO ₂ were charged into a super mixer, stirred at 300 to 400 rpm for about 30 seconds, While stirring, 2,850 g of paraffin oil was added, and the mixture was further stirred at 300 to 400 rpm for about 2 to 3 minutes to prepare a mixture.

The mixture was poured into a twin-screw extruder (screw diameter = 32 mm, L / D = 56, twin screw extruder) at a rate of about 80 g / min and melted and kneaded at about 215 캜 and 130 rpm to form a T- die ).

The melts discharged through the T-die were cast at approximately 0.9 m / min (about 120 m / min of the Ti die discharge speed) at a casting roll of about 80 DEG C consisting of steel rolls and nip rolls spaced apart from each other by about 0.3 mm before solidification %) To form a sheet having a thickness of 0.31 mm. At the same time, the sheet was stretched and then passed through a cooling roll at about 30 캜 to solidify the sheet.

The sheet was passed at a rate of about 0.9 m / min at a calender roll of about 130 DEG C spaced apart by about 0.3 mm to adjust the pore size of the sheet, and the surface was polished.

Thereafter, the sheet was immersed in a dichloromethane leaching tank adjusted to 25 ° C, and paraffin oil was extracted and removed for 10 minutes. The sheet from which the paraffin oil was removed was passed through a drying roll at 60 DEG C and dried to prepare a vapor permeable membrane having a thickness of 0.3 mm. The average pore diameters in the surface area (about 50 m from both surfaces of the sheet) and the central area (excluding the surface area) of the prepared vapor permeable membrane were measured to be about 54 nm and about 80 nm, respectively.

Example 2

The vapor permeable membrane was prepared in the same manner as in Example 1, except that the casting roll was operated at an operating speed of about 1.125 m / min (about 150% of the Ti die discharge rate). The average pore diameters in the surface area and central area of the vapor permeable membrane prepared were measured to be about 58 nm and about 140 nm, respectively.

Example 3

The vapor permeable membrane was prepared in the same manner as in Example 1 except that the casting roll was operated at an operating speed of about 1.5 m / min (about 200% of the Ti die discharge rate). The average pore diameters in the surface region and central region of the prepared vapor permeable membrane were measured to be about 60 nm and about 200 nm, respectively.

Example 4

The vapor permeable membrane was prepared in the same manner as in Example 1, except that the casting roll was operated at an operating speed of about 0.825 m / min (about 110% of the Ti die discharge rate). The average pore diameters in the surface area and central area of the vapor permeable membrane prepared were measured to be about 53 nm and about 70 nm, respectively.

Example 5

A vapor permeable membrane was prepared in the same manner as in Example 1, except that the operating speed of the casting roll was changed to about 0.75 m / min (the same as the Ti die discharge rate). The average pore diameters in the surface area and central area of the vapor permeable membrane prepared were measured to be about 52 nm and about 65 nm, respectively.

Comparative Example

A vapor permeable membrane was prepared in the same manner as in Example 1 except that the casting roll was operated at an operating speed of about 0.675 m / min (about 90% of the Ti die discharge rate). The average pore diameters in the surface region and the central region of the prepared vapor permeable membrane were measured to be about 100 nm and about 103 nm, respectively.

Experimental Example

The holder assembly used for evaporation rate and performance testing of the vapor permeable membrane consisted of a front clamp with a ring gasket, a rear clamp, a plastic storage cup and four screws. The plastic storage cup has an internal dimension defined by a circular diameter at the edge of the opening of about 4 cm and a depth of less than 1 cm. The open area was used to measure volatile material migration rate.

Each clamp of the holder assembly has a 3.8 cm diameter circular opening to receive the storage cup and to provide an opening for exposing the membrane under test. When placing the vapor permeable membrane, the rear clamp of the holder assembly was placed on top of the cork ring. The storage cup was placed in the rear clamp and filled with about 2 mL of benzyl acetate. A disk of about 5.1 cm diameter was cut from the vapor permeable membrane and placed in contact with it directly over the edge of the storage cup to expose the volatile material contact of the 12.5 cm ² vapor permeable membrane into the interior of the storage cup.

The front clamp of the holder was placed on the entire assembly, but the screw holder was aligned so that the vapor permeable film was not dispersed. Attach the screws and tighten them sufficiently to prevent leakage. The ring gasket produced a seal. Labs were attached to verify the vapor permeable membrane samples in the test and 5 to 10 replicate verifications were prepared for each test.

The weight of each holder assembly was measured to determine the initial weight of the fully charged assembly and the assembly was placed inside the laboratory hood. With the storage cup upright, the benzyl acetate contacts at least a portion of one side of the vapor permeable membrane. The glass door of the hood was also pulled down, the air flow through the hood was adjusted to 8 revolutions (or turnover) of the hood volume per hour, and the hood temperature was maintained at 25 +/- 5 deg. The weight of the holder assembly was measured once a day for 5 days to determine the rate of benzyl acetate movement through the vapor permeable membrane in terms of surface area, elapsed time, and calculated weight loss of benzyl acetate (unit: mg / (hour * cm &lt; ² &gt;) were measured (mean value over 5 days). The average evaporation rate (mg / hr) of benzyl acetate was calculated using the following formula 1, and the results are shown in Table 1 below.

&Quot; (1) &quot;

Average evaporation rate (mg / hr) / 12.5 cm ² = volatile transfer rate (mg / (hour * cm ² ))

division Average Evaporation Rate Example 1 5.1 Example 2 4.8 Example 3 4.2 Example 4 5.9 Example 5 6.0 Comparative Example 7.2

Referring to Table 1, in Examples 1 to 5 having an average pore diameter gradient of about 5 nm or more in the thickness direction, the average evaporation rate is slower than the comparative example having substantially no average pore diameter gradient.

When the average pore diameter in the central region of the vapor permeable membrane is larger than that in the surface region as in Examples 1 to 5, the volatile substance introduced through one surface of the vapor permeable membrane does not flow out immediately through the other surface, And the volatile substance is completely carried on the central region, and then flows out to the air through the other surface. That is, when the volatile substance is completely carried in the central region of the vapor permeable membrane, the amount of volatile material flowing in and the amount of flow of the volatile substance reach the steady state, that is, substantially steady state, Lt; / RTI &gt;

On the other hand, in the case of the comparative example having substantially no average pore diameter gradient, the volatile substance introduced through the one surface of the vapor permeable membrane is immediately discharged into the air through the other surface without being supported by the central region.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: surface porous layer
200: medium porous layer

Claims (15)

An intermediate porous layer, and a surface porous layer disposed on at least one side of the intermediate porous layer,
Wherein the average pore diameter d ₁ of the intermediate porous layer and the average pore diameter d ₂ of the surface porous layer satisfy the following conditions (i) and (ii)
The vapor permeable membrane having a d ₂ of 60 nm or less,
(i) d ₁ > d ₂ ,
(ii) d ₁ - d ₂ ≥ 5 nm. The method according to claim 1,
Wherein the intermediate porous layer and the surface porous layer are integrally formed. The method according to claim 1,
Wherein the vapor permeable membrane comprises a polyolefin-containing resin composition. The method of claim 3,
Wherein the polyolefin is one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and mixtures or copolymers of two or more of the foregoing. 5. The method of claim 4,
Wherein the polyolefin is an ultrahigh molecular weight polyethylene having a weight average molecular weight of 200,000 to 1,000,000 and an intrinsic viscosity of 5.0 dl / g or more. The method according to claim 1,
The vapor permeable membrane having a d ₁ of 65 to 300 nm. The method according to claim 1,
Wherein the vapor permeable membrane has a thickness of 20 to 1200 占 퐉. 8. The method of claim 7,
And the thickness of the surface porous layer is 1 to 50% of the thickness of the vapor permeable film. (a) extruding a resin composition comprising a polyolefin and a pore-forming agent, discharging the resin composition through a Ti-die, and passing the resin composition through a casting roll to produce a base sheet;
(b) passing the base sheet through a calender roll to impart a gradient to an average pore diameter along a thickness direction of the base sheet; And
(c) immersing the base sheet in a solvent to remove the pore forming agent,
Wherein the operation speed of the casting roll is 1.0 to 2.0 times the discharge speed of the Ti-die. 10. The method of claim 9,
Wherein the polyolefin is one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and mixtures or copolymers of two or more thereof. 10. The method of claim 9,
Wherein the polyolefin is an ultrahigh molecular weight polyethylene having a weight average molecular weight of 200,000 to 1,000,000 and an intrinsic viscosity of 5.0 dl / g or more. delete 10. The method of claim 9,
Wherein the average pore diameter along the thickness direction of the base sheet in the step (b) satisfies the following (i) and (ii):
(i) d ₁ > d ₂ ,
(ii) d ₁ - d ₂ ≥ 5 nm,
In (i) and (ii) above,
d ₁ is the average pore diameter of the intermediate porous layer,
and d ₂ is the average pore diameter of the surface porous layer located on at least one side of the intermediate porous layer. 10. The method of claim 9,
Wherein the pore former is selected from the group consisting of paraffin oil, paraffin wax, mineral oil, solid paraffin, soybean oil, rapeseed oil, palm oil, palm oil, di-2-ethylhexyl phthalate, dibutyl phthalate, diisononyl phthalate, diisodecyl phthalate, bis Heptyl) phthalate, naphthenic oil, and mixtures of two or more thereof. 10. The method of claim 9,
Wherein in the step (c), the solvent is one selected from the group consisting of pentane, hexane, benzene, dichloromethane, carbon tetrachloride, methyl ethyl ketone, acetone and a mixture of two or more thereof.

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